linux-kernel - Re: [PATCH 3/6] block: Create scsi

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Date:   Thu, 24 May 2018 00:36:54 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        Jens Axboe <axboe@...nel.dk>,
        Christoph Hellwig <hch@...radead.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Tejun Heo <tj@...nel.org>, Borislav Petkov <bp@...en8.de>,
        "David S. Miller" <davem@...emloft.net>,
        "Manoj N. Kumar" <manoj@...ux.vnet.ibm.com>,
        "Matthew R. Ochs" <mrochs@...ux.vnet.ibm.com>,
        Uma Krishnan <ukrishn@...ux.vnet.ibm.com>,
        linux-block <linux-block@...r.kernel.org>,
        linux-ide@...r.kernel.org, linux-scsi@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/6] block: Create scsi_sense.h for SCSI and ATAPI

On Wed, May 23, 2018 at 02:17:14PM -0700, Kees Cook wrote:
> 
> True, though I'm finding other robustness issues in the CDROM code.
> They're probably all insane corner cases, but it seems like it'd be
> nice to just fix them:
> 
> diff --git a/drivers/cdrom/cdrom.c b/drivers/cdrom/cdrom.c
> index 3522d2cae1b6..7726c8618c30 100644
> --- a/drivers/cdrom/cdrom.c
> +++ b/drivers/cdrom/cdrom.c
> @@ -2222,9 +2223,12 @@ static int cdrom_read_cdda_bpc(struct
> cdrom_device_info *cdi, __u8 __user *ubuf,
> 
>                 blk_execute_rq(q, cdi->disk, rq, 0);
>                 if (scsi_req(rq)->result) {
> -                       struct request_sense *s = req->sense;
> +                       struct scsi_sense_hdr sshdr;
> +
>                         ret = -EIO;
> -                       cdi->last_sense = s->sense_key;
> +                       scsi_normalize_sense(req->sense, req->sense_len,
> +                                            &sshdr);
> +                       cdi->last_sense = sshdr.sense_key;
>                 }
> 
>                 if (blk_rq_unmap_user(bio))

The proper fix here is to rewrite this function to use the the
->generic_packet cdrom_device_ops method.  Is is the only caller
going straight to the scsi passthrough requests, which is a layering
violation.